Respiration-related movements of the nose in dogs.

We studied the respiration-related movements of the canine nose by examining the respiratory oscillations of intranasal balloon pressure and EMG activities of the dilator nares in dogs. Under spontaneous respiration, balloon pressure decreased and EMG activities increased during the early inspiratory phase. These respiratory movements of the nose differed and changed reciprocally in strength between the two sides of the body spontaneously, after painful stimulation or intranasal histamine administration. When the muscle relaxant was administered and the respiration was controlled by the ventilation pump, the intranasal balloon pressure increased during the inspiratory phase. This phenomenon had a completely inverted pattern compared with that during spontaneous respiration. Furthermore, even when the ventilation pump was stopped, respiration-like spontaneous oscillations of the intranasal balloon pressure were recognized. These were abolished by sectioning of the ipsilateral cervical sympathetic nerve trunk. From these findings, the respiration-related movements of the nose were thought to be controlled not only by the cardiac output and the vagal nerve reflexes but also by respiratory activities in the nervous systems controlling the nose, which might be originated from the medullary respiratory centres.